Apparatus and method for learning gear ratio control of CVT

Abstract

An apparatus for learning gear ratio control of a CVT (Continuously Variable Transmission) may include: an APS (Acceleration Position Sensor) configured to detect a change of an accelerator pedal in a CVT vehicle; a gear ratio detector configured to detect a pulley gear ratio of the CVT; a timer configured to measure the time during which gear ratio control learning is performed during power-off up-shift of the CVT; and a controller configured to receive the values detected through the APS, the gear ratio detector and the timer, and control the CVT to shift gears at a target gear ratio learned through the gear ratio control learning, during the power-off up-shift by coasting.

What is claimed is: 
     
       1. An apparatus for learning gear ratio control of a CVT (Continuously Variable Transmission), comprising:
 an APS (Acceleration Position Sensor) configured to detect a change of an accelerator pedal in a CVT vehicle; 
 a gear ratio detector configured to detect a pulley gear ratio of the CVT; 
 a timer configured to measure a time during which gear ratio control learning is performed during power-off up-shift of the CVT; and 
 a controller configured to receive values detected through the APS, the gear ratio detector and the timer, and control the CVT to shift gears at a target gear ratio learned through the gear ratio control learning, during the power-off up-shift by coasting. 
 
     
     
       2. The apparatus of  claim 1 , wherein the learned target gear ratio indicates a target gear ratio by which a slope indicating a time required to reach the target gear ratio with respect to a current gear ratio is adjusted to a gentle or steep slope, in order to prevent a rapid change of the current gear ratio when the current gear ratio is controlled to follow the target gear ratio. 
     
     
       3. The apparatus of  claim 1 , wherein the controller checks whether an APS change is smaller than a preset APS value or a change of the target gear ratio is smaller than a preset gear ratio change, and determines a time point of the power-off up-shift by coasting. 
     
     
       4. The apparatus of  claim 1 , wherein during the power-off up-shift by coasting, the controller enters the gear ratio control learning, captures a current gear ratio and the target gear ratio, and operates the timer to check a gear shifting time. 
     
     
       5. The apparatus of  claim 4 , wherein when an absolute value of a difference between a target gear ratio corresponding to the current driving situation and a target gear ratio captured at the point of time to enter the gear ratio control learning is smaller than a first gear ratio, the controller continuously increases a timer value to check the gear shifting time while the learning is performed, the gear shifting time indicating a time period from a learning start to a learning end time. 
     
     
       6. The apparatus of  claim 5 , wherein the controller compares the absolute value of the difference between the current gear ratio and the target gear ratio captured at the point of time to enter the gear ratio control learning to a second gear ratio, compares the timer value to a first preset timer value when it is determined that the current ratio approaches the target gear ratio captured at the point of time to enter the gear ratio control learning within a preset range, determines that the pulley gear ratio was too early changed when the timer value is smaller than the first preset timer value, and controls a slope of the learned target gear ratio to a slope lower than a slope of the target gear ratio. 
     
     
       7. The apparatus of  claim 6 , wherein when the timer value is between the first preset timer value and a second preset timer value, the controller determines that the pulley gear ratio was changed at a designated time, and maintains the slope of the learned target gear ratio at the current slope. 
     
     
       8. The apparatus of  claim 7 , wherein when the timer value is larger than the second preset timer value, the controller determines that the pulley gear ratio was changed after the designated time, and increases the slope of the learned target gear ratio to a slope close to the target gear ratio. 
     
     
       9. The apparatus of  claim 4 , wherein when an absolute value of a difference between a target gear ratio corresponding to a current driving situation and a target gear ratio captured at the point of time to enter the gear ratio control learning is larger than a first gear ratio, the controller determines that the power-off up-shift by coasting terminates, and stops the gear ratio control learning. 
     
     
       10. A method for learning gear ratio control of a CVT, comprising:
 detecting, by an APS, a change of an accelerator pedal in a CVT vehicle; 
 detecting, by a gear ratio detector, a pulley gear ratio of the CVT; 
 measuring, by a timer, a time during which gear ratio control learning is performed, during power-off up-shift of the CVT; and 
 receiving, by a controller, values detected through the APS, the gear ratio detector and the timer, and controlling the CVT to shift gears at a target gear ratio learned through the gear ratio control learning during the power-off up-shift by coasting. 
 
     
     
       11. The method of  claim 10 , wherein in order to determine a power-off up-shift point by coasting, the controller checks whether the APS change is smaller than a preset APS value, and a change of the target gear ratio is smaller than a preset gear ratio change. 
     
     
       12. The method of  claim 10 , wherein during the power-off up-shift by coasting, the controller enters the gear ratio control learning, captures a current gear ratio and the target gear ratio, and operates the timer to check a gear shifting time. 
     
     
       13. The method of  claim 12 , wherein when an absolute value of a difference between a target gear ratio corresponding to the current driving situation and a target gear ratio captured at the point of time to enter the gear ratio control learning is smaller than a first gear ratio, the controller continuously increases a timer value to check the gear shifting time while the learning is performed, the gear shifting time indicating a time period from a learning start point to a learning end time. 
     
     
       14. The method of  claim 13 , wherein the controller compares the absolute value of the difference between the current gear ratio and the target gear ratio captured at the point of time to enter the gear ratio control learning to a second gear ratio, compares the timer value to a first preset timer value when it is determined that the current ratio approaches the target gear ratio captured at the point of time to enter the gear ratio control learning within a preset range, determines that the pulley gear ratio was too early changed when the timer value is smaller than the first preset timer value, and controls a slope of the learned target gear ratio to a slope lower than a slope of the target gear ratio. 
     
     
       15. The method of  claim 14 , wherein when the timer value is between the first preset timer value and a second preset timer value, the controller determines that the pulley gear ratio was changed at a designated time, and maintains the slope of the learned target gear ratio at the current slope. 
     
     
       16. The method of  claim 15 , wherein when the timer value is larger than the second preset timer value, the controller determines that the pulley gear ratio was changed after the designated suitable time, and increases the slope of the learned target gear ratio to a slope close to the target gear ratio. 
     
     
       17. The method of  claim 12 , wherein when an absolute value of a difference between a target gear ratio corresponding to a current driving situation and a target gear ratio captured at the point of time to enter the gear ratio control learning is larger than a first gear ratio, the controller determines that the power-off up-shift by coasting terminates, and stops the gear ratio control learning.